1. Describe the structure and function of a neuron.
Answer:
A neuron is the basic functional unit of the nervous system. It consists of three main parts:
- Cell Body: Contains the nucleus and other organelles, responsible for maintaining the cell’s metabolic activities.
- Dendrites: These are tree-like extensions that receive signals from other neurons or sensory receptors.
- Axon: A long, slender projection that transmits electrical impulses away from the cell body to other neurons, muscles, or glands. The neuron’s primary function is to carry nerve impulses throughout the body, allowing communication between different body parts and the central nervous system (CNS).
2. Explain the differences between the central nervous system (CNS) and the peripheral nervous system (PNS).
Answer:
The Central Nervous System (CNS) includes the brain and spinal cord. It processes and interprets sensory information, makes decisions, and sends instructions to the PNS.
The Peripheral Nervous System (PNS) consists of nerves and ganglia located outside the CNS. It connects the CNS to limbs and organs. The PNS is responsible for transmitting sensory information to the CNS and relaying motor commands to muscles and glands.
3. What is the role of the brain in the nervous system of vertebrates?
Answer:
The brain is the central organ of the nervous system in vertebrates. It is involved in processing sensory information, coordinating movement, regulating homeostasis, and controlling behavior. The brain has specialized regions for different functions:
- The cerebrum is responsible for higher functions such as thinking, memory, and decision-making.
- The cerebellum controls coordination and balance.
- The medulla oblongata regulates basic life functions such as heartbeat and breathing.
4. Describe the structure and function of the spinal cord.
Answer:
The spinal cord is a long, cylindrical structure composed of neurons that extends from the brainstem down to the lower back. It serves as the main pathway for transmitting information between the brain and the rest of the body. The spinal cord is protected by vertebrae and meninges. It has two primary functions:
- Transmission of sensory and motor information between the body and brain.
- Reflex actions, as it can process certain stimuli without involving the brain, such as withdrawing a hand from a hot surface.
5. What are glial cells, and what role do they play in the nervous system?
Answer:
Glial cells are non-neuronal cells that provide support and protection to neurons. They play a crucial role in maintaining the environment of neurons, forming myelin sheaths, and assisting with the repair of damaged tissues. There are several types of glial cells, including:
- Astrocytes: Provide structural support and regulate blood-brain barrier function.
- Oligodendrocytes: Form myelin sheaths in the CNS.
- Schwann cells: Form myelin sheaths in the PNS.
- Microglia: Act as the immune cells of the nervous system.
6. Explain the process of action potential in neurons.
Answer:
An action potential is an electrical signal that travels along the axon of a neuron. It is generated when a neuron’s membrane potential becomes more positive, reaching a threshold level. This causes voltage-gated sodium channels to open, allowing sodium ions to rush into the cell, depolarizing the membrane. This is followed by the opening of potassium channels, allowing potassium ions to flow out, repolarizing the membrane. The action potential travels down the axon to the synaptic terminal, where neurotransmitters are released into the synapse to transmit the signal to the next neuron.
7. What is the significance of the blood-brain barrier?
Answer:
The blood-brain barrier (BBB) is a selective permeability barrier that protects the brain from harmful substances in the blood, such as toxins and pathogens. It is formed by endothelial cells in blood vessels that are tightly joined, preventing large or harmful molecules from crossing into the brain. The BBB allows essential nutrients like glucose and oxygen to pass through while blocking harmful substances. This barrier helps maintain the brain’s delicate chemical balance and ensures proper neural function.
8. Differentiate between the sympathetic and parasympathetic divisions of the autonomic nervous system.
Answer:
The sympathetic nervous system (SNS) is responsible for the “fight or flight” response, preparing the body for stressful situations by increasing heart rate, dilating pupils, and inhibiting digestion. It uses norepinephrine as its primary neurotransmitter.
The parasympathetic nervous system (PNS), on the other hand, is responsible for the “rest and digest” functions, promoting relaxation, slowing the heart rate, and stimulating digestion. It uses acetylcholine as its primary neurotransmitter.
9. What is the role of neurotransmitters in the nervous system?
Answer:
Neurotransmitters are chemical messengers that transmit signals across synapses from one neuron to another or from neurons to muscles or glands. When an action potential reaches the synaptic terminal of a neuron, neurotransmitters are released into the synapse. They bind to receptor sites on the postsynaptic neuron, either exciting or inhibiting it. Common neurotransmitters include dopamine, serotonin, acetylcholine, and norepinephrine.
10. What is the role of the hypothalamus in regulating body functions?
Answer:
The hypothalamus is a small but crucial part of the brain that plays a key role in maintaining homeostasis. It regulates essential body functions such as temperature, hunger, thirst, and circadian rhythms. The hypothalamus also controls the pituitary gland, which regulates hormone production throughout the body. Additionally, it plays a role in emotional responses and autonomic functions such as heart rate and blood pressure.
11. How does the nervous system facilitate reflex actions?
Answer:
Reflex actions are automatic, rapid responses to stimuli that do not require conscious thought. These actions are processed in the spinal cord, bypassing the brain. When a sensory receptor detects a stimulus, a signal is transmitted through a sensory neuron to the spinal cord, where it is relayed to a motor neuron. The motor neuron then transmits the signal to an effector (muscle or gland) to elicit a response, such as pulling a hand away from a hot object. This quick pathway helps protect the body from harm.
12. Describe the structure of the meninges and their role in the nervous system.
Answer:
The meninges are three protective layers of tissue that surround the brain and spinal cord. These layers include:
- Dura mater: The outermost and toughest layer, providing a protective barrier.
- Arachnoid mater: The middle layer, which is a web-like structure filled with cerebrospinal fluid.
- Pia mater: The innermost layer, which closely adheres to the surface of the brain and spinal cord. These layers help protect the central nervous system from physical damage and infections, and the cerebrospinal fluid cushions the brain and spinal cord.
13. What is the function of the cerebellum in vertebrates?
Answer:
The cerebellum is responsible for coordinating voluntary movements, balance, and motor control. It receives information from sensory systems, the spinal cord, and other parts of the brain to regulate posture, muscle coordination, and fine motor movements. The cerebellum ensures that movements are smooth and precise, and it also helps in the learning of motor skills, such as riding a bicycle or playing an instrument.
14. Explain how the peripheral nervous system contributes to sensory and motor functions.
Answer:
The peripheral nervous system (PNS) includes sensory neurons that carry signals from sensory receptors to the central nervous system (CNS) and motor neurons that transmit instructions from the CNS to muscles and glands.
- Sensory functions: The PNS receives stimuli from the environment (e.g., light, sound, touch) and transmits these signals to the brain for interpretation.
- Motor functions: The PNS carries signals from the brain to muscles and glands to initiate movement or secretion. The PNS is further divided into the somatic nervous system (voluntary control) and the autonomic nervous system (involuntary control).
15. Describe the role of the thalamus in sensory processing.
Answer:
The thalamus is a critical relay station in the brain that processes sensory information. It receives inputs from sensory organs (except smell) and directs them to the appropriate regions of the cerebral cortex for further processing. The thalamus plays an essential role in sensory perception, alertness, and sleep-wake cycles. It filters and prioritizes sensory signals, allowing the brain to focus on relevant stimuli while ignoring less important information.
16. What are the different types of neurons and their functions?
Answer:
Neurons are classified into three types based on their function:
- Sensory neurons: Transmit sensory information from receptors (e.g., skin, eyes) to the CNS.
- Motor neurons: Carry motor commands from the CNS to muscles and glands.
- Interneurons: Connect sensory and motor neurons within the CNS, processing information and coordinating responses.
17. How do myelin sheaths enhance nerve impulse transmission?
Answer:
Myelin sheaths are fatty layers that surround axons, acting as insulation and increasing the speed of nerve impulse transmission. Myelination allows for faster conduction of action potentials by enabling the electrical signal to jump from one node of Ranvier (gaps in the myelin) to the next, a process known as saltatory conduction. This significantly enhances the efficiency of nerve communication.
18. Explain the concept of “plasticity” in the nervous system.
Answer:
Neuroplasticity refers to the ability of the nervous system to reorganize itself by forming new neural connections. This process occurs in response to learning, experience, or injury. Neuroplasticity allows the brain to adapt to new situations, recover from damage (to a certain extent), and strengthen neural pathways through repeated use, making it a vital aspect of brain development and rehabilitation.
19. What are the functions of the autonomic nervous system?
Answer:
The autonomic nervous system (ANS) regulates involuntary physiological functions such as heart rate, digestion, respiration, and blood pressure. It is divided into two branches:
- Sympathetic nervous system (SNS): Activates the “fight or flight” response during stressful situations, increasing heart rate, dilating pupils, and inhibiting digestion.
- Parasympathetic nervous system (PNS): Promotes “rest and digest” activities, slowing heart rate and enhancing digestion.
20. Discuss the role of the medulla oblongata in life-sustaining functions.
Answer:
The medulla oblongata is a critical structure at the base of the brainstem that controls autonomic functions essential for life, including heart rate, breathing, and blood pressure regulation. It also plays a role in reflex actions such as swallowing, coughing, and vomiting. Damage to the medulla can be life-threatening due to its involvement in vital functions.
